Nanoscale iron particles are increasingly attracting interest as efficient sorbents for various types of pollutants from aqueous solutions and effluents. In the present study, nanoparticles were prepared by a coprecipitation method and then characterized by X-ray diffraction, transmission electron microscopy, Fourier transformation IR spectroscopy, and vibrating sample magnetometry. The diameters of the nanopartides were in the range (10 to 15) nm. The adsorption of Ni(II) and Cr(VI) from diluted aqueous solutions onto Fe(3)O(4) nanoparticles was investigated. The parameters studied include contact time and concentration of the metal ions. Iron nanoparticles demonstrated very rapid uptake of these metal ions. The adsorption was found to be highly dependent on solution pH. Cr(VI) removal was found to be greater in the acidic range while Ni(II) removal was greater in the basic range of solutions. Increasing the temperature increased the removal of both metal ions, indicating the endothermic nature of the system. Langmuir and Freundlich isotherm constants were determined and revealed that magnetic nanoparticles can serve as efficient adsorbents for the removal of Ni(II) and Cr(VI). These data can be used in the design of a treatment plant on an industrial scale.